The present invention concerns an arrangement for cleaning gaseous atmosphere from a plurality of separate, contained working spaces by means of removal of noxious, in particular radioactive, gases, such as tritium, with an individual gas circuit containing a circulating pump for each working space.
Large tritium laboratories comprise the most varied experimental devices, each of which is housed in its own contained working space ("containment"), such as a glove box, a caisson and the like. These containments are operated in part at atmospheric pressure and in part under a vacuum; they may contain plain air, a purified atmosphere (air from which the oxygen and/or any possible humidity has been removed), or an inert gas, such as a rare gas.
The experiments or operating devices installed in the working spaces contain, in general, varying tritium quantities, and their hazard potential varies likewise. Examples of such differing devices are all-metal apparatus, systems with open sample-taking, electrolytic cells with a high probability that tritiated water vapors are set free, tempered metal getters whereby T-permeation or leakage may occur, just to mention a few examples.
The atmosphere of such contained working spaces is constantly monitored for reasons of safety and is processed through installations for tritium removal, whereby there must be taken into consideration so-called normal releases (release of tritium through permeation, leakage, maintenance, taking of samples) as well as breakdown release (sudden release of the entire tritium stock).
A method is known whereby each containment is provided with its own device for tritium removal which is adjusted individually to the prevailing circumstances, i.e., it is designed specifically in consideration, e.g., of throughput, T-absorption ability, servicing interval and risk potential for the working space concerned and the experimental and operating installations contained therein. This solution, however, is very costly in that for each working space there must be provided separate blowers or fans, compressors, reactors, absorption sections, filters, heat exchangers, regulating and control organs, etc.
The installation effort may be decreased by a central tritium removal system which is connected with several or all contained working spaces of the laboratory. Such a central system, however, must answer the requirements of all working spaces, namely: the atmosphere (e.g., air, inert gas, rare gas, with or without oxygen, with or without moisture); the pressure conditions (overpressure, vacuum, atmospheric pressure, low or high flow rate); the danger potential (kind of experiment and of the outer containment, such as metallic, open, etc.); and the tritium content (quantity calculated absolutely), condition of the aggregate (gaseous or bound with solid or liquid substances), etc. From this it follows that a central system must be operated with a great variety of operating states. This drastically increases the number of the regulating and control organs for pressure, temperature, flow rate, added-gas metering, etc., and large throughput and pressure ranges are required for the fans, blowers and compressors. The control of catalytic converters, the dimensioning of absorption sections, of filters and separators must comprise wide ranges which can be covered only with difficulty by process engineering. Therefore, a central system is complex and intricate, the safety conditions are hard to determine and are therefore easily planned in an unrealistic manner, while breakdowns and failures of the system can be controlled only with difficulty.
Similar problems also occur in other plants in which radioactive or other noxious gases must be removed from separate working spaces.